1. Field of the Invention
The present invention is directed to a synergistic herbicidal composition having an enhanced speed-up or acceleration in its post-emergent herbicidal activity against grassy weeds. In particular, the present invention is directed to a herbicidal composition containing a herbicidally effective amount of the compound 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one or a herbicidally effective salt thereof. This compound is a known pre-emergent and post-emergent herbicide having herbicidal activity against grassy weeds. The composition of the present invention further contains the compound 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazine-6-yl]-4,5, 6,7-tetrahydro-1H-isoindole-1,3-(2H)-dione in an amount effective to accelerate the post-emergent herbicidal activity of 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one or its salt. The present invention is based upon my discovery that the compound 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazine-6-yl]-4,5, 6,7-tetrahydro-1H-isoindole-1,3(2H)-dione unexpectedly and synergistically interacts with the compound 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one or its salt to provide for a marked acceleration in the herbicidal activity of this latter compound against grassy weeds.
2. Description of the Related Art
U.S. Pat. Nos. 4,640,707 and 4,792,605 describe the compound 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazine-6-yl]-4,5, 6,7-tetrahydro-1H-isoindole-1,3(2H)-dione; compounds related thereto; the preparation of such compounds; and the fact that these compounds possess herbicidal activity. In practice, while the compound 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazine-6-yl]-4,5, 6,7-tetrahydro-1H-isoindole-1,3(2H)-dione has shown excellent herbicidal activity against dicotyledonous weeds, this compound possesses poorer post-emergent herbicidal activity against grassy weeds such as johnsongrass (sorghum halepense), etc.
Reissue U.S. Pat. No. 32,489 as well as European Patent Application No. 85/904 773 and International Patent Application WO 87/01699 disclose compounds such as 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one (and salts thereof, see also U.S. Pat. No. 4,741,768 for suitable salts) as well as disclose that these compounds possess pre-emergent and post-emergent herbicidal activity against grassy weeds. In practice, while the compound 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one (and its salts) possesses excellent herbicidal activity against grassy weeds, this compound has little or no activity against dicotyledonous weeds. Additionally, the post-emergent herbicidal activity of this compound against grassy weeds manifests itself over an extended period of time. Thus, when a herbicidally effective amount of this compound is applied against grassy weeds, a suitable high level of kill of such weeds, e.g., generally greater than 90%, usually occurs about 7-21 days after application. While this delay between application and the resulting high levels of kill may in some circumstances be acceptable or even desirable, there are also circumstances where it would be desirable for the herbicidal activity of this compound to be accelerated. For example, in no-till planting of crops such as soybeans, peanuts, corn, etc., it is common practice for the seeds to be planted either shortly before or shortly after the application of a herbicidal composition designed to completely kill all of the existing weeds without the prior tilling of the soil to remove these weeds. In this circumstance, it would be desirable for a rapid burndown (kill) of all of the weeds so that the germinating crop seeds as well as the resulting seedlings do not have competition from these weeds for soil moisture and nutrients. Such a rapid burndown should preferably occur within 5 days after application of the herbicidal composition and even more preferably within 3 days. Accordingly, it is an object of this invention to provide for a herbicidal composition containing 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one (or its salt) in which the post-emergent herbicidal activity of this compound against grassy weeds is accelerated so that this compound could be more effectively used in herbicidal compositions employed in no-till planting.
While it is common practice to attempt to design a herbicidal composition having a broad spectrum of herbicidal activity by combining two or more herbicides with limited activity, i.e., combining a herbicide having activity against grassy weeds with a herbicide having activity against dicotyledonous weeds, such compositions often do not result in the desired herbicidal activity. This result is attributed to some sort of antagonism between the herbicidal compounds.
Accordingly, it is a further object of this invention to provide for a herbicidal composition having two or more herbicidal components which results in a complete burndown of both grassy and dicotyledonous weeds with little or no antagonism between the herbicidally active components. It is still a further object of this invention to provide for a herbicidal composition which results in the rapid burndown of grassy weeds as well as dicotyledonous weeds so that this composition could be used in no-till planting.
These and other objects are achieved by the compositions of the present invention which provide for a composition containing both the compound 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propynyl)-2H-1,4-benzoxazine-6-yl]-4,5, 6,7-tetrahydro-1H-isoindole-1,3(2H)-dione and the compound 2-[1-(3-trans-chloroallyloxyimino)propyl]-5-(2-ethylthiopropyl)-3-hydroxy- 2-cyclohexen-1-one (or a herbicidally effective salt thereof). In regard to this composition, none of the above cited references disclose this combination.